An 86-year-old woman who had been treated for tuberculous peritonitis and pulmonary tuberculosis, exhibited a disturbance of consciousness and tonic-clonic convulsions seven days after the administration of the antituberculous drug isoniazid. As her serum vitamin B6 level was remarkably low, she was diagnosed with convulsive seizures due to vitamin B6 deficiency associated with isoniazid treatment. Seizures refractory to standard anticonvulsant therapy were controlled with the administration of pyridoxine. Most reported cases of isoniazid-induced convulsive seizures occurred as a result of an overdose due to attempted suicide. This report presents a case of convulsive seizures that occurred in association with the short-term administration of a therapeutic dose of isoniazid.